Long-term Debt and Capital Lease Obligations (Details) (USD $) In Thousands, unless otherwise specified	6 Months Ended	12 Months Ended
	Jun. 30, 2014	Dec. 31, 2013
Debt Instrument [Line Items]
Long-term debt gross	$ 289,444	$ 290,611
Less current installments	3,121	5,242
Long-term debt and capital lease obligations, less current installments	286,323	285,369
Fixed interest rate (in hundredths)	7.375%
Second Priority Senior Secured Notes [Member]
Debt Instrument [Line Items]
Long-term debt gross	250,000	0
Term Loan Under Credit Agreement, Variable [Member]
Debt Instrument [Line Items]
Long-term debt gross	0	222,750
Revolver Under Credit Agreement, Variable [Member]
Debt Instrument [Line Items]
Long-term debt gross	9,000	36,000
Missouri IRBs [Member]
Debt Instrument [Line Items]
Long-term debt gross	7,548	7,756
Fixed interest rate (in hundredths)	2.80%	2.80%
Capital Leases [Member]
Debt Instrument [Line Items]
Long-term debt gross	13,951	14,572
Capital Leases [Member] | Minimum [Member]
Debt Instrument [Line Items]
Fixed interest rate, minimum (in hundredths)	2.04%	2.04%
Capital Leases [Member] | Maximum [Member]
Debt Instrument [Line Items]
Fixed interest rate, maximum (in hundredths)	7.73%	7.73%
Notes Payable [Member]
Debt Instrument [Line Items]
Long-term debt gross	$ 8,945	$ 9,533
Notes Payable [Member] | Maximum [Member]
Debt Instrument [Line Items]
Fixed interest rate, maximum (in hundredths)	3.60%	3.60%